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排序方式: 共有964条查询结果,搜索用时 93 毫秒
741.
Junjuan Shao Jianbo Shi Bu Duo Chengbin Liu Yan Gao Jianjie Fu Ruiqiang Yang Guibin Jiang 《环境科学学报(英文版)》2016,28(1):22-28
As a global pollutant, high levels of mercury (Hg) have been found in remote ecosystem due to the long range atmospheric transport. In this study, a total of 60 fish samples were collected from four rivers across the Tibetan Plateau to study the accumulation of Hg in remote and high-altitude aquatic environment. The total Hg (THg) and methylmercury (MeHg) in fish muscles ranged from 11 to 2097 ng/g dry weight (dw) (average: 819 ng/g dw) and from 14 to 1960 ng/g dw (average: 756 ng/g dw), respectively. Significantly positive linear relationships were observed between the THg (r = 0.591, p < 0.01, n = 36) and MeHg concentrations (r = 0.473, p < 0.01, n = 36) with the trophic level of fish from Lhasa River, suggesting trophic transfer and biomagnification of Hg in this aquatic ecosystem. Moreover, the THg levels in fish had significantly positive correlations with the length (r = 0.316, p < 0.05, n = 60) and weight (r = 0.271, p < 0.05, n = 60) of fish. The high levels of Hg were attributed to the slow growth and long lifespan of the fish under this sterile and cold environment. Risk assessment revealed that the consumption of Oxygymnocypris stewartii, Schizothorax macropogon, Schizothorax waltoni, Schizopygopsis younghusbandi and Schizothorax o'connori would lead to a high exposure to MeHg. 相似文献
742.
为了提高高炉干法除尘布袋的寿命,在重力除尘器和布袋除尘器之间加入旋风除尘装置,得到的旋风灰可以作为煤粉添加剂。对首秦高炉旋风灰进行粒度和化学成分分析,研究发现高炉旋风灰可以降低煤粉着火温度,提高燃烧效率,且其粒度分布与喷吹煤粉相似,可以作为高炉喷吹煤粉添加剂。通过实验室测定煤粉添加不同比例旋风灰后的燃烧率,确定在富氧率为3%,旋风灰添加比例为6%的条件下,可达到最佳的煤粉燃烧效果。旋风灰作为高炉自产的喷煤添加剂,与煤粉混合喷吹可以为企业减轻固废处理负担,同时带来可观的经济效益和社会效益。 相似文献
743.
744.
To investigate the influences of alkaline pretreatment on anaerobic digestion (AD) and sludge dewaterability after AD, waste activated sludge was adjusted to different pH values (8, 9, 10, 11, 12) and placed at ambient temperature for 24 hr. The samples were then adjusted to the initial pH and subjected to 25 days of AD. The results showed that, when compared with the control (pH 6.8), total suspended solids (TSS) and volatile suspended solids (VSS) reduction following pretreatment at pH 9-11 increased by 10.7%-13.1% and 6.5%-12.8%, respectively, while biogas production improved by 7.2%-15.4%. Additionally, significant enhancement of sludge dewaterability after AD occurred when pretreatment at pH 8-9 was conducted. The proteins and carbohydrates transferred from the pellet and tightly bound extracellular polymeric substances (TB-EPS) fractions to the slime and loosely bound EPS (LB-EPS) fractions after pretreatment and during the AD process, and the concentrations of proteins and carbohydrates in the slime fraction had a good linear relationship with the normalized capillary suction time (CST). During the AD process, the normalized CST was positively correlated with the organic materials in the loosely bound fraction of the sludge matrix (R2≥qslant 0.700, p < 0.01), while it was negatively correlated with the organic materials in the tightly bound fraction (R2≥qslant 0.702, p < 0.01). These results suggest that alkaline pretreatment could break the EPS matrix and release inner organic materials, thus influencing the efficiency of the AD process and dewaterability after AD. 相似文献
745.
The rapid development of the fluorinated pesticide industry has produced a large amount of fluorine-containing hazardous waste, especially inorganic fluoride-containing waste (IFCW). A two-step process, including extraction and recovery, was developed to recover fluorine as synthetic cryolite from IFCW produced by the pesticide industry. The optimum conditions for extraction were found to be a temperature of 75°C, an initial pH (pHi) of 12, a 4-hr incubation time and a liquid-to-solid ratio of 40 mL/g; these conditions resulted in a fluorine extraction ratio of 99.0%. The effects of pH and the F/Al molar ratio on fluorine recovery and the compositional, mineralogical and morphological characteristics of the cryolite products were investigated. Field-emission scanning electron microscopy of recovered precipitates showed changes in morphology with the F/Al molar ratio. Coupling Fourier transform and infrared spectroscopy, X-ray diffraction indicated that the formation of AlF63 − was restricted as increasing pH. Both the amount of fluorine recovered and the quality of the cryolite were optimized at initial pH = 3 and a F/Al molar ratio 5.75. This study proposed a reliable and environmentally friendly method for the treatment of fluoride-containing wastes, which could be suitable for industrial applications. 相似文献
746.
747.
北京市西北城区取暖期环境大气中PM10的物理化学特征 总被引:17,自引:2,他引:17
根据监测资料探讨了北京市西北城区取暖期PM10的逐日变化规律和日变化规律.分别使用X射线衍射仪(XRD)和扫描电镜(SEM)研究PM10中的矿物成分及其微观形貌特征.结果表明夜间PM10浓度普遍高于白天.XRD分析显示颗粒物粒度越细,其中所含的矿物种类越少.SEM研究得出,单个PM10颗粒类型可初步分为有链状集合体、簇状集合体、圆球状、片状和不规则形状等5类.从数量上看,PM10主要来自燃煤和汽车尾气. 相似文献
748.
749.
China’s new Classification-Based Forest Management (CFM) is a two-class system, including Commodity Forest (CoF) and Ecological
Welfare Forest (EWF) lands, so named according to differences in their distinct functions and services. The purposes of CFM
are to improve forestry economic systems, strengthen resource management in a market economy, ease the conflicts between wood
demands and public welfare, and meet the diversified needs for forest services in China. The formative process of China’s
CFM has involved a series of trials and revisions. China’s central government accelerated the reform of CFM in the year 2000
and completed the final version in 2003. CFM was implemented at the provincial level with the aid of subsidies from the central
government. About a quarter of the forestland in China was approved as National EWF lands by the State Forestry Administration
in 2006 and 2007. Logging is prohibited on National EWF lands, and their landowners or managers receive subsidies of about
70 RMB (US$10) per hectare from the central government. CFM represents a new forestry strategy in China and its implementation
inevitably faces challenges in promoting the understanding of forest ecological services, generalizing nationwide criteria
for identifying EWF and CoF lands, setting up forest-specific compensation mechanisms for ecological benefits, enhancing the
knowledge of administrators and the general public about CFM, and sustaining EWF lands under China’s current forestland tenure
system. CFM does, however, offer a viable pathway toward sustainable forest management in China. 相似文献
750.
Involvements of chloride ion in decolorization of Acid Orange 7 by activated peroxydisulfate or peroxymonosulfate oxidation 总被引:1,自引:0,他引:1
The effects of Cl- on the decolorization of AO7 by SO4·- based-peroxydisulfate or peroxymonosulfate oxidation under various activated conditions were different. 相似文献